Blueair Pro L Particle Air Purifier Filter Genuine Blueair replacement particle filter designed to fit the Blueair Pro M, L, XL air purifiers Patented HEPASilent technology quietly captures 99.97% of harmful airborne particles such as pollen, smoke, bacteria, viruses, pet dander, dust, and harmful pollutants down to 0.1 microns The gradient filter structure is designed to maximize capture of airborne particles, while trapping the particulates and preventing them from being re-released back into the air. Filter fibers are free from chemicals Polypropylene filter materials are 100% recyclable and naturally anti-bacterial to prevent mildew and mold growth Whisper silent design is supported by use of low density media that allows high air flow and lower air pressure, augmented with electrostatic charge to capture particles